Food-treatment devices are known having a muffle in which is provided a heater and blower. The blower circulates gases in the oven in a closed path over the heater, which may be of the electrical resistance type or a gas burner, so as evenly to distribute the heated gases throughout the muffle. Such an arrangement is conventionally used in large commercial installations where convection alone cannot be relied on for adequate heat distribution throughout the muffle.
Such an arrangement, although extremely effective in the large-scale production of roasted goods, baked goods, and the like, does have the disadvantage that certain kinds of foodstuffs are damaged by the constantly circulating gases. Thus flaky pastry, streusel or the like can be damaged by the circulated gases. Nonetheless in such systems it is absolutely necessary to circulate the gases as the heaters are placed in a position where they would be ineffective to heat the muffle without the forced-air circulation. Other types of foodstuffs are also disadvantageously dried out by excessive gas circulation.